Great advances in hearing assistive technology in recent years have improved the lives of many hearing impaired individuals and enabled people to hear better, or in some cases, to hear at all. Various hearing assistive devices exist for alleviation of different conditions. Among these devices is a type of device known as a cochlear implant.
Cochlear implants are generally intended for certain people with profound hearing loss. In a typical cochlear implant user, the function of the inner ear is severely degraded, and therefore the condition does not respond well to conventional hearing appliances, which simply amplify the sound entering the ear canal. A cochlear implant by-passes the inner ear to transmit sound directly to the cochlea. A variation of the cochlear implant is an auditory brainstem implant, which is an implantable device placed near the junction of the cochlea and auditory nerve, to by-pass even the cochlea where appropriate.
Generally, a cochlear or other implantable hearing assistive device comprises a surgically implanted portion and an externally worn portion. The externally worn portion is a digital electronic device receiving power from a battery, and containing a microphone, amplification, filtering and/or sound processing electronics, and a transmitter. The externally worn portion may be packaged as multiple components, but at least a portion of it is worn in close physical proximity to the ear. The implanted portion receives signals representing sounds transmitted by the transmitter of the externally worn portion, and contains an electrode or electrodes for stimulating the cochlea or auditory nerve. The implanted portion is a passive energy device containing no independent power source (it being expected to last for years in its surgically implanted position). When the externally worn portion is properly positioned for use, it is electromagnetically coupled with the implanted portion and supplies power to the implanted portion through the electromagnetic coupling.
A variety of everyday devices emit audible alarm or informational signals to alert individuals to some danger or condition which may require attention. Examples include fire or other emergency condition alarms, telephones, doorbells, alarm clocks, etc. If an individual having an implanted hearing assistive device is wearing the external portion and it is functioning normally, the individual should be able to hear most everyday audible alarms. However, most persons with cochlear implants or similar devices remove the externally worn portion at least part of the time. For example, the externally worn portion is often removed while sleeping, both for reasons of comfort, and to avoid inadvertent damage to the unit while sleeping. It is also typically removed while bathing, and sometimes may be removed purely for relaxation, to shut out externally distracting noise. If an audible alarm sounds at a time when the individual has removed the externally worn portion, he will not hear the alarm. This fact poses inconvenience to individuals with implantable devices, and, particularly where they are sleeping, exposes them to additional danger as a result of the fact that they can not hear audible fire alarms and the like.
Various alarm systems have been proposed for hearing impaired individuals, but in general these suffer certain drawbacks, particularly when applied to a profoundly deaf person with cochlear or other implanted devices. The external portion of the cochlear implant hearing assistive device is normally removed when sleeping, deactivating the device. Because these individuals are profoundly deaf, they are generally immune to auditory alarms when asleep, even when the alarms are extremely loud. Some alarm systems rely on flashing lights or other visual stimuli, either alone or in combination with auditory stimuli, but many people do not respond reliably to visual stimuli when asleep. Vibrating alarms also exist, but these must be worn close to the body to ensure that the user will detect vibration; they may be uncomfortable or not necessarily be reliably sensed by the user when asleep, particularly if the device shifts position during sleep.
It would of course be possible for the hearing impaired individual to simply wear the external portion of the cochlear implant when asleep, but for many users this is impractical. It may be uncomfortable or difficult to sleep with the device in the ear. Furthermore, the device can easily fall out due to the user's movements while asleep, which would both render any alarm ineffective and subject the device to risk of loss or damage. These devices are quite expensive, and most users will not wish to risk damage to the devices. Additionally, removal of the device while sleeping allows moisture, which may accumulate in the device due to its proximity to the human body, to evaporate; this is believed to prolong the life of the device. Some manufacturers recommend that they be removed while sleeping for this reason.
A need exists for improved techniques to warn and/or inform certain individuals with profound hearing loss of dangers or other conditions, and particularly, for techniques which will be effective even in the absence of an externally worn unit for supplying a signal to an implantable device.